Inheritance, variation and evolution

• Allele: An alternative form of a gene
• Asexual reproduction: The production of offspring from a single parent by mitosis, resulting in clones of the parent
• Chromosome: Structures in the nucleus that contain the DNA of an organism
• Cystic fibrosis: A disorder of cell membranes caused by a recessive allele
• DNA: A polymer made up of two strands forming a double helix
• Dominant: An allele that is always expressed, even if only one copy is present
• Fertilisation: The fusion of male and female gametes
• Gamete: Sperm cell and egg cell in animals; pollen and egg cell in plants
• Gene: A small section of DNA that codes for a specific protein
• Genome: The entire genetic material of an organism
• Genotype: The combination of alleles
• Heterozygous: A genotype with two different alleles - one dominant and one recessive
• Homozygous: A genotype with two of the same alleles, either two dominant or two recessive alleles
• Meiosis: A two-stage process of cell division that reduces the chromosome number of daughter cells, producing gametes for sexual reproduction
• Mutation: A change in DNA
• Phenotype: The characteristic expressed due to the combination of alleles
• Polydactyly: Having extra fingers or toes, caused by a dominant allele
• Recessive: An allele that is only expressed if two copies are present
• Sexual reproduction: The production of offspring by combining genetic information from the gametes of two parents, leading to variation in the offspring
• Embryo screening: Genetic tests on an embryo to check for faulty alleles
• Evolution: A change in inherited characteristics of a population over time through natural selection
• Evolutionary tree: A method showing how scientists believe organisms are related
• Extinction: The permanent loss of all members of a species
• Fossils: Remains of organisms from millions of years ago found in rocks
• Genetic engineering: The manipulation and change of an organism's genotype by scientists
• Natural selection: The process where organisms better suited to an environment are more likely to survive and reproduce
• Selective breeding: Humans selecting animals or plants with desired characteristics for breeding
• Speciation: The process where two species evolve from a single original species by natural selection, becoming so different they can no longer interbreed
• Variation: Differences in characteristics of individuals in a population
• Mitosis: Produces two genetically identical daughter cells, the cell divides once, used for growth, repair, and asexual reproduction
• Meiosis: Produces four genetically different daughter cells, the cell divides twice, produces gametes for sexual reproduction
• Sex determination: Females carry two X chromosomes, males carry one X and one Y chromosome
• How to complete a Punnet Square: Shows the probability of offspring inheriting different combinations of alleles
• Advantages of sexual reproduction: Produces variation in offspring, gives a survival advantage via natural selection, can be increased by humans in selective breeding
• Advantages of asexual reproduction: Only one parent needed, more time and energy efficient, faster than sexual reproduction, many identical offspring can be produced under favorable conditions
• Resistant Bacteria: Antibiotic-resistant strains can be reduced by proper antibiotic use and restrictions in agriculture
• Evolution by Natural Selection: All species have evolved from simple life forms by natural selection, advantageous variants are more likely to survive and reproduce
• Variation: Differences in genes, environment, or a combination of both leading to variation in populations
• Isolation, conditions, natural selection, speciation: Parts of a population become isolated, different conditions lead to advantageous characteristics, organisms with these characteristics survive and pass on alleles, eventually leading to speciation
• DNA Structure: Double helix structure with nucleotides containing phosphate, sugar, and base pairs (C-G, A-T)